Gas phase filter media for odor adsorption have long been used in many applications. Typical applications may include ductless range hood filters, air cleaner filters and filter systems for air conditioning, heating and ventilating systems. Offensive odors normally involved include those such as generated by cooking, pets or human waste.
Particulate filter media, such as expanded aluminum, fiber glass or the like may be combined with a gas phase odor adsorption media if the given application also requires removal of particulate matter.
One of the most common media forms employed for odor adsorption includes a bed of activated carbon particles. This type of filter media consists of some form of a bed of activated carbon particles supported in a given manner between appropriate layers of other media or a metal frame to form a compartment to contain the particles in the desired configuration.
Examples of such gas phase filters are disclosed in U.S. Pat. Nos. 3,630,007; 2,544,733; 3,873,287 and 3,645,072.
These carbon bed filters present two disadvantages in typical air movement systems. Often the pressure drop through the filter is too large for economical operation and generally such filters are relatively expensive to manufacture and fabricate. Another disadvantage in certain types of carbon beds is the tendency for the particles to settle and form a non-uniform filter media path.
Another form of gaseous filter media for odor control in disclosed in U.S. Pat. No. 4,227,940 and consists of a perforated sheet of metal or laminate material in which carbon particles are bonded to the sheet in a relatively random manner. The perforations are created by merely punching holes in the sheet upon which the carbon particles are adhesively bonded. This type of filter is designed for use in moving air systems in which pressure drop through the filter is an important consideration.
Another type of filter media is disclosed in U.S. Pat. No. 3,870,495 and comprises a non woven laid fiber material for use in filters.
Among the considerations important in filter applications of the type mentioned above is the balance achieved between efficiency of odor removal, resistance to air flow and cost of manufacture. Generally, in prior art constructions, improvement in odor removal efficiency and capacity is off-set by an increase in air flow resistance and results in a higher pressure drop. This creates an increase in the operating cost of the system in addition to an increase in the manufacturing cost of the filter media.
The prior art media employing carbon bonded to a metal or laminate sheet provided with holes, while achieving a degree of success and market acceptance, is less than fully satisfactory in achieving an improved relationship between removal efficiency, resistance to air flow and cost of manufacture.